Thread: Progress on My Unimog

My transmission is a bit special - I have 8 speeds in the main box, a "low range" working gears, and a Claas overdrive gear splitter behind the engine giving 23% overdrive. So in theory I have 32 speeds forward, and 32 speed backwards.

In practise, getting from low to high range is a bit tricky - but it's not something you really need to do often - 1st gear is quite a low gear and 1st gear low range is 500m/hour at 2000rpm I will be able to match winch speeds with the working gears quite easily.

The 8 speed box is really 2x 4 speeds. Getting from 4-5 is a bit slow, as there is a pneumatic ram has to change over from one planetary gear set to the other to give you the upper 4 speeds. The normal 4 speed is quick and easy, however the overdrive is really quick - just a flick of the switch.

In sand I would be in 2nd or 3rd gear with the overdrive on, to drop down 23% would be a matter of pressing the clutch and the trigger on the gear lever. However - with the torque band of the big diesel and the 365/80-20 tyres which I can run at 0 psi due to the bead locks I should be able to get through fairly soft sand. I have a mate with a U1300 who had no trouble going up Big Red last year, and I have better tyres, more power and less weight.

Might as well update the thread whilst the Blues are getting slaughtered

Fabricated up the exhaust system this weekend - 3" all the way and not many bends - it's a total length of 4.7m long as it has to go all the way out the back of the truck. I've put flanges all the way along to make it easier to get out. All I need now is to find a silencer of the right shape and size.

It should be a great improvement on the old one.

Iain, I hate you cause I'm jealous. I want a Unimog now. You don want a hand do you, I would love to help, just for the experience...... Ha I wish.

Very interesting thread, always looking forward to it.

Geck

All help would be appreciated - anyone know much about fitting hydraulic brake lines

If anyone wants to come over for a chat or just to see the truck, just contact me.

Just a few more progress photos, this weekend saw the mail fuel tank getting fitted, and the start of construction of the rear storage pods. The photo shows the framework in place but because I ran out of welding wire - so I used all my clamps - 6 welding clamps, 6 quickgrip clamps , three g-clamps and 4 of those weird red handle type clamps - it goes to show, you can never have enough clamps

If anyone is interested in buying a very good Ex-army Unimog - drop me a pm and I'll put you in contact with the guy who owns three of these beauties.

I learnt a bit about bearings this week.

I'm fitting new hub gears into the portal axles - the gears ( and Claas overdrive) will let me drive at 100kph at 2200rpm. When I stripped down the left hand portals, I checked the bearings and there was no scoring or wear marks at all, everything was really tight so I thought I could save money by just cleaning, putting in new seals and re-fitting the bearings. There are 4 large bearings and the total cost per corner would be around $400 from the overseas Unimog places.

Then I stripped down the right hand portals - and discovered that the bearings were badly pitted. One the inner lower bearing, it looked like someone had taken a grinder to the bearing. The open roller bearing was also worn - but suspect it was particles from the failure inner bearings that caused the problem. The outer bearings are a special open race roller bearing - OEM spares only, but the inner ones were normal bearings - FAG and SKF ones - those I thought I could get locally. On one website there was mention of a roller bearing superseding the ball bearing - so I thought I would try and find them.

I contacted the bearing places, read off the numbers and they found suitable matching ball bearings, but could not find the roller bearings - but the price was real good - way cheaper than the overseas bearings.

That made me suspicious, so with help from a friend that has a whole series of bearing handbooks, we looked up the relevant bearing and looked for the new roller bearings - that's when we discovered that there were "heavy duty" or "E " or "R" mark bearings. Checking the load ratings on those we found that these heavy duty bearings had about 30-50% more load capacity than the "standard" range.

A bit more checking and examination of photos of OEM bearing that had failed and I realised that what is supposed to be in the portals are all the heavy duty "E" or "R" class bearings. The ones that were in the front portal were all standard class bearing, and I suspected the ones in the left hand portals were also standard bearings.

I took them apart and found them all the others were the lower grade bearings. Judging by the messy silicone seal used all over the portals, it looks like some time in the past, the good mechanics at NSW Railcorp had re-done the portals, but saved a bit on money by only using OEM parts on the open race bearings (if they replaced them at all) and just used the off-the-shelf local bearings - but they didn't replace one of them. I don't think the 8.2 ton load, and the 150mm offset on the wheels needed to get the tyres right on the rail tracks helped either. I can understand why - local suppliers charge $1490 per corner for the bearings and seals - I've just paid $375 per corner to get them from the UK.

In one way I am quite lucky - I found out about it the easy way - a bit of extra labour and a few weeks of waiting is all it will cost me in the end. If the right hand bearings had not failed then I would have just re-assembled the portals and I could guarantee that the failure would have been at a very inconvenient place - like the middle of the Gobi desert.

Anyway, now I'm replacing all the bearings and seals, and with the new gears, the only thing that is left of the original axles are the housings.

Just a quick update. All the portals are now assembles, and I've started on the brake lines and air line.

Blknight helped out with a cab lifter and we got the cab upright - now that's what I call access to an engine - you can almost walk around the thing now.

I'll be running the new airlines, paint the underside properly, making new heat shields and maybe get the exhaust manifold etc coated with that ceramic paint to keep the heat out the cab.

Hey Iain - what progress in the last month?

Cheers
David